For many avid walkers and runners, side stitches can be a problem. The cramplike spasms set in suddenly and can ruin a good workout. While no one knows their precise cause, many experts believe a side stitch occurs when the diaphragm — which is vital to breathing — is overworked during a vigorous walk or run and begins to spasm. Runners who develop stitches are commonly advised to slow down and take deep, controlled breaths.

But a new theory suggests that it may not be the diaphragm that’s responsible for the pain, and that poor posture could be a culprit. In one recent study, researchers used a device to measure muscle activity as people were experiencing side stitches. They found no evidence of increased activity or spasms in the diaphragm area during the onset of stitches.

One explanation is that poor form may affect nerves that run from the upper back to the abdomen. Another is that hunching increases friction on the peritoneum, a membrane that surrounds the abdominal cavity. This could also explain why controlled breathing seems to help relieve stitches: drawing deep breaths fills the lungs and improves posture.

Focus on bending your knees and pushing your butt out when you are exercising. Doing those two things will correct your posture and keep your breathing in your diaphragm and under control.